The Forever Moving Land

The land below us is always in motion. Plate tectonics studies these
restless effects to give us a better understanding of the Earth and its past.
New molten rocks are poured out in the form of magma from the mid-ocean ridges.
The rock is recycled and re-entered back into the earth in deep ocean trenches
through convection current. The convection current in the mantle drives plates
around either against or away from each other. These collisions give rise to
earthquakes, volcanoes, mountains, and continental drift. The crashing and
spreading of the plates forms the landscape of the Earth as we see it today.
The positions of the land masses today is a result of continental drift. ...

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that still exists today. The immense heat from the magma (approximately
2700(C) causes convection in the mantle (Figure 1). Convection is caused by
non-uniform temperature in a fluid and density differences. This continuous
convection is the cause of plate movement. Each complete cycle, called a
convection cell, drives the plate in the direction of the cell. How does a
'solid' mantle move? The mantle may be solid but, as with most solids, it will
deform if long term stress is applied; "...like Silly Putty which seeps into
the rug when left unattended, mantle material flows when subjected to small
long-term stresses."1
Presently, there are more than fourteen plates in the Earth's crust
(Figure 22). Upwelling hot magma flows out from mid-ocean ridges and then cools
down when exposed to the cooled environment outside; the layer of cooled magma
forms the lithosphere. When magma flows out from the ridges, the crust is
fractured and a new ocean floor is built spreading ...

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accepted today, however. There was
abundant evidence for Wegener to believe in the existance of Pangea. The shape
of the continents could be pieced together like a giant jigsaw puzzle suggesting
that the continents were once 'glued' together. The fossils found on the
continents were not distinct to that particular land, but were also found in
lands that were separated by thousands of kilometers of water. Fossils
indicated that identical species existed in different continents. Geological
structures also demonstrated that the continents were, in fact, one giant land
mass; old mountain ranges from one continent matched with those from another
(i.e., South America and Africa).
Ocean ...

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